I agree. But also, Muslims took down the World Trade Center, so . . . .
...they also have religious fanatics who would impose their religion on others. American Muslims, as you know, are somewhat less inclined to want their religion imposed on the rests of us, than American Christians are.
So we need to be more wary of fanatics from other countries than of our fellow Americans.
Apparently, the vetting works pretty well; the FBI has shown that you are far more likely to be taken out by an American-born terrorist than by an immigrant.